Organically based animal litter and manufacturing process

ABSTRACT

The present disclosure provides a lightweight hybrid clumping animal litter made from organic core particles combined with small amounts of clumping agent, and methods for making the litter.

TECHNICAL FIELD

This invention relates to animal litter compositions and relatedmanufacturing methods.

BACKGROUND

Animal litters such as cat litter have been made out of a variety ofabsorbent materials. Early litter compositions used non-gelling ornon-clumping clays, such as montmorillonite and attapulgite. Later,gelling clays, such as sodium bentonite, were used to absorb urine wasteinto a removable clump. The ability to scoop out all solid wastetogether with clumps of litter containing urine provided a cleanerlitter box and reduced odor.

Litters made entirely from clay such as sodium bentonite have high bulkdensities, in the range of 50-65 lbs/cu-ft., making them heavy andtherefore difficult and costly to handle, package and transport.Attempts to address this problem by encapsulating particles of lighterweight clays with a coating of heavy, clumping clay like sodiumbentonite have produced only marginal reduction in bulk density, to onlyslightly less than about 60 lbs/cu-ft. Also, the clump formation orstrength of the clump for litters primarily made with sodium bentonitemay be reduced due to salts and other constituents in animal and inparticular cat urine that affect the gelling or clumping of these typesof litters.

As an alternative to clays, certain plant-based, organic materials havebeen used to prepare absorbent granules, which can provide litter ofsomewhat lower bulk densities. Such materials also have the advantage ofproviding a recycling stream for materials normally treated as a wasteby-product. Examples of such organic materials are wheat grain andby-products from wet milling of corn. Such organic materials howevergenerally do not exhibit good clumping performance, even when containingstarch, which has some limited function as a clumping promoter.

SUMMARY

In one aspect, the present disclosure provides a clumping animal littercomprising: core particles comprising about 50% to about 85% by weightof an organic substrate, about 0.01% to about 10.0% by weight of abinding agent impregnating the organic substrate, and about 10% to about40% by weight of a clumping agent, optionally further comprising apolysaccharide gum or a borated starch comprising about 1% to about 3%by weight of the litter composition. Wherein the binding agent binds theclumping agent to the core particles, and wherein the ratio of organicsubstrate to total clumping agents is about 4 to 1. The core particleshave an external surface and optionally pores in the external surface,and the binding agent is non-uniformly distributed over the externalsurface and optionally in the pores of the core particles. The clumpingagent can comprise, for example, no more than about 20% by weight of thelitter. The organic substrate can comprises a non-agglomerated, hardgranular, granulized or pelletized organic material. The organicsubstrate can be selected from the group consisting of corn cob, cornmeal, soybean, soybean meal, wheat meal, wheat straw, alfalfa meal,peanut hulls, rice hulls, walnut shells, paper, paper sludge, pinesawdust, diaper fluff, and any combination thereof. In an exemplarylitter, the organic substrate comprises corncob grit. The core particlesof organic substrate can have a size of about 8 mesh to about 40 mesh(about 2.4 mm to about 0.4 mm); a size of about 10 mesh to about 40 mesh(about 2.0 mm to about 0.4 mm); a size of about 14 mesh to about 20 mesh(about 1.4 mm to about 0.8 mm); or a size of about 14 mesh to about 40mesh (about 1.4 mm to about 0.4 mm).

In the litter, the binding agent can comprise for example an aqueoussolution of an adhesive compound, or an adhesive compound which isliquid at room temperature. The adhesive compound can be selected from apolyvinyl alcohol, guar gum, tara gum, xanthan gum, a hydrocolloid gum,sodium alginate, a latex, a starch, corn syrup, corn syrup solids, andany combination thereof. The adhesive compound can be for example acombination of sodium alginate with at least one polysaccharide otherthan sodium alginate.

When the binding agent comprises an adhesive compound in aqueoussolution, the concentration of the adhesive compound in the aqueoussolution can be for example about 0.1% to about 5%, about 0.1% to about10%, about 0.1% to about 75%, or about 0.1% to about 99%, by weight. Inthe litter, the ratio of adhesive compounds to the organic material inthe litter can be less than about 15% by weight. The litter can have amoisture content of no more than about 10% to about 20% by weight,preferably no more than about 10% to about 12% by weight.

In the litter, the clumping agent can comprise for example a materialselected from a gelling clay such as attapulgite, bentonite, kaolinite,sepiolite, a borated polysaccharide gum, and a borated starch, or anycombination thereof. In an exemplary litter composition, the clumpingagent comprises sodium bentonite. The borated polysaccharide gum can befor example a borated gum selected from sodium alginate, guar gum, taragum, xanthan gum, locust bean gum, cassia gum, carboxymethyl cellulose.A borated starch can be for example borated wheat starch or boratedpotato starch.

An exemplary clumping animal litter can comprise about 10% to about 40%by weight sodium bentonite and further comprises a combination of sodiumalginate gum and sodium borate in a weight-to-weight ratio of about 80%to about 85% sodium alginate gum to about 15% to about 20% borate. Insuch a clumping animal litter, the sodium alginate and sodium borate canbe combined in a weight to weight ratio of about 85% sodium alginate gumto 15% borate, wherein the combination of sodium alginate and sodiumborate comprises about 1% to about 3% by weight of the littercomposition.

A clumping animal litter as described herein can further comprise anodor control agent comprising about 5% or less by weight of the littercomposition. The binding agent can further bind the odor control agentto the core particles, along with clumping agent(s). The odor controlagent can comprise at least one odor absorbent material, for example anodor absorbent material selected from natural and synthetic zeolites,sodium bicarbonate, and magnesium hydroxide, or at least one odormasking fragrance, or any combination thereof.

In another aspect, the present disclosure provides a method of preparinga clumping animal litter from organic material, the method comprising,in the following order: obtaining granulized particles of an organicmaterial; spraying the organic particles with an aqueous solutioncomprising a binding agent to impregnate the organic particles with thebinding agent; mixing the organic particles and the powdered clumpingagent for a time sufficient for the clumping agent to adhere to thesurface of the organic particles, in amounts such that the organicsubstrate comprises about 50% to about 85% by weight of the litter, thebinding agent comprises about 0.01% to about 10.0% by weight of thelitter, and the clumping agent comprises about 10% to about 40% byweight of the litter; and drying the organic particles to apredetermined moisture content. In the method, the clumping agent cancomprise sodium bentonite. The clumping agent can comprise apolysaccharide gum or a borated starch, in an amount such that thepolysaccharide gum or borated starch comprises about 1% to about 3% byweight of the litter composition. In the method, the ratio of the amountof organic substrate to the amount of clumping agent in the litter canbe about 2 to 1, about 2.5 to 1, about 3 to 1 or about 4 to 1. In themethod, the organic substrate can comprise a non-agglomerated, hardgranular, granulized or pelletized organic material, such as for examplecorncob grit. Alternatively, the organic material can be selected fromcorn cob, corn meal, soybean, soybean meal, wheat meal, wheat straw,alfalfa meal, peanut hulls, rice hulls, walnut shells, paper, papersludge, pine sawdust, diaper fluff, and any combination thereof.

The core particles of organic material can have any size as describedabove for the clumping animal litter, such as for example a size ofabout 8 mesh to about 40 mesh, about 10 mesh to about 40 mesh, about 14mesh to about 20 mesh, or about 14 mesh to about 40 mesh. In the method,the clumping agent(s), binding agent(s), adhesive compound(s), odorcontrol agent(s), weight ratios of the different components, and allcomponents can be as described above for the clumping animal litter. Themethod can provide a clumping animal litter with a predeterminedmoisture content of less than about 20% by weight, less than about 15%by weight, or less than about 8-12% by weight. An exemplary litter has amoisture content of no more than about 10% to about 20% by weight,preferably no more than about 10% to about 12% by weight.

The method can further comprise screening the dried organic particles toobtain particles in a size range of about 10 mesh to about 40 mesh,about 10 mesh to about 40 mesh, about 14 mesh to about 20 mesh, or about14 mesh to about 40 mesh, and optionally further comprise at least oneof i) adding excess fines less than about 40 mesh back into the mixingstep; and ii) remilling particles having a size greater than about 10mesh to produce remilled particles having a size of less than about 10mesh and adding the resultant remilled particles back into the mixingstep. The present disclosure also encompasses a clumping animal litterproduced according to any of the methods described herein, and having adensity of about 20 lbs/cu-ft to about 35 lbs/cu-ft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of clumping agent particles scatteredon the surface of core particles of organic material.

FIG. 2 is a schematic illustration of the clumping agent and coreparticles of organic material agglomerated together to form a hardened,removable clump.

FIG. 3 is a flow chart of a first method for manufacturing a hybridclumping animal litter.

FIG. 4 is a flow chart of a second method for manufacturing a hybridclumping animal litter.

DETAILED DESCRIPTION

The hybrid clumping animal litter described herein is prepared from coreparticles of plant derived, organic materials and a clumping agent thatdoes not segregate from the absorbent litter granules, thus providing alightweight, less costly clumping animal litter which also provides away to recycle organic waste materials into useful product. In contrastto conventional clumping litters that consist exclusively or primarilyof an inorganic clumping agent such as bentonite or another clumpingclay, the clumping litter described herein combines organic materialswith an inorganic clumping agent, and thus can be considered a “hybrid”clumping litter. The result is a clumping litter that has the absorbentproperties of the plant derived organic litter substrate, and a lowdensity due to the organic substrate. The hybrid clumping litter has arelatively low density of about 20 to about 35 lbs/cu-ft. In addition,the clumping litter does not have dust or ingredient segregation issues,is economical to produce, and is primarily made from recycling amaterial that would normally be considered a waste product.

A hybrid clumping animal litter is for example composed of coreparticles of organic, absorbent material, each impregnated with aclumping agent, and a binding agent that binds the clumping agent to theorganic material particles/granules. An exemplary litter includes thecore particles (or “substrate”), the binding agent for binding clumpingagents to the core particles, the clumping agent, and optionally aclumping aid to help speed up clump formation.

An exemplary clumping agent comprises an inorganic material such assodium bentonite. As used herein, the term “impregnated” meanspermeated, such that particles of the clumping agent are distributed onthe surface of, and optionally further in pores of the core particles oforganic material. As shown in FIG. 1, the clumping agent does not form acontinuous or complete coating or encapsulate the core particles, butrather is distributed over the surface of the core particles in a mannerwhich can be described as “decorating” the surface of the particles.This arrangement has been discovered by the inventors to strike ahelpful balance between providing suitable clumping capability, andminimizing the use of an otherwise heavy clumping agent such as sodiumbentonite. As the granules absorb moisture, interstitial bonding occursbetween the surfaces of the inorganic clumping agent material andorganic hybrid granules to form a clump. FIG. 2 is a schematic diagramof a hybrid litter composition after clumping of the hybrid granulesfollowing exposure to moisture, such as occurs when the animal urinecontacts the dry litter composition. FIG. 2 shows essentiallyhomogeneous agglomerated clumps of multiple individual core particles oforganic material having a comparatively small amount of clumping agentdistributed over the surface of the particles, without forming asubstantially continuous coat on the particles. The inventors havefurther found that a clumping agent comprising both a clumping agentsuch as sodium bentonite and a further clumping aid or additive such asa borated starch or a polysaccharide gum, results in even fasterformation and hardening of litter clumps than would otherwise beachieved using only the limited amounts of a clumping agent such assodium bentonite. At the same time, the litter minimizes use ofpolysaccharide gums or borated starches, which are costly. Further, thebinding agent can also further promote clumping upon contact with animalurine. The inventors have further discovered certain methods forpreparing a hybrid litter to overcome various problems resulting fromattempts to combine clumping agents and clumping agent combinations asdescribed herein with organic materials.

Organic materials used for the core particles can be, for example,corncob corn meal, wood (e.g. pine) chips or sawdust, soybean, soybeanmeal, wheat meal, wheat straw, alfalfa meal, walnut shells, peanuthulls, rice hulls, wheat straw, paper or paper sludge, diaper fluff, orany combination thereof.

The particles can be any shape, such as spherical, elliptical,elongated, flat, or some other irregular shape. Preferably the materialsare available as, or can be prepared as hard particles or granules orpellets. The particles should however not be agglomerated. It will beappreciated by those of routine skill in the art that a “hard” pellet orgranule is firm, not easily friable, and can be handled in a mixer suchas a rotating mixer, sprayed with an aqueous adhesive solution, and havepowdered clumping agents attached to it, without disintegrating.Exemplary such particles would generate no more than about 1% fines ordust from mixing the substrate granules prior to adding the ingredients.Agglomerated particles are thus not suitable for the hybrid clumpinglitter. A rotating mixing process can be used to accomplish the mixingas detailed further below.

Core particles can be manufactured, in non-limiting example, fromcorncob. A hard corncob grit or firm corncob grit is preferred, ratherthan the chaff (i.e., “bee's wings”) or softer parts of the corncob thathave a lower density compared to corncob grit. The use of corncob gritresults in a suitably hard surface, as compared to other particles madefrom softer materials, for applying the binding agent and clumpingagent(s). Material that easily flies away, such as the chaff, is alsodifficult to spray with the binding agent and results in tracking, i.e.,carrying of litter particles out of the litter box on the cat's fur orpaws, which is a typical problem with most other litters. Additionally,corncob grit exhibits excellent absorbent properties, being capable ofabsorbing up to about 120% its weight in water. Other organic materialssuch as peanut hulls and soybean hulls can exhibit comparably highabsorbency.

Corncob grit is derived from the hard middle woody ring of the corncob.An animal litter can contain for example about 100% of the organic coreparticles as corncob grit. The corncob grit is obtained by grinding thewoody ring of the corncob into particles. Similarly, any organicmaterials used for the core particles can be ground or otherwisegranularized according to many methods well known in the art. Forexample, 8×40 mesh granules that are suitable for spraying with thebinding agent solution can be made by grinding organic material such aspeanut hulls and/or soybean hulls to a powder, making pellets in apellet mill, and then crumbling the pellets to obtain particles of thedesired size as detailed below.

The binding agent is applied to the hard external surface of the coreparticles, for example by spraying. It will be appreciated that certainorganic materials are porous and when they are used, the binding agentcan be applied in such a manner, e.g., by spraying, that the bindingagent distributes at least partially in at least a portion of the pores,and thus allows for at least partial binding of the clumping agent insome of the pores.

Core particles can be, for example, no larger than about 8 mesh (about2.4 mm), and preferably no larger than about 10 mesh (about 2.0 mm). Anexample of a clumping animal litter uses particles as small as about 40mesh (about 0.4 mm). A suitable range of core particle sizes is thusabout 8 mesh to about 40 mesh. Another suitable range of core particlesizes is about 14 mesh to about 20 mesh, or about 1.4 mm to about 0.8mm. Another suitable range of core particle sizes is about 14 mesh toabout 40 mesh, or about 1.4 mm to about 0.4 mm. It will be recognizedhowever that particles larger than about 8 mesh can be used, for exampleparticles as large as ⅛ inch (3.175 mm) can be used, but that the largergranules tend to form much larger clumps and are more difficult toremove without breaking apart in the litter box. Further, larger clumpsoften stick to the bottom of the litter box and break apart uponremoval, leaving pieces of soiled litter that contribute to odor. Thus,the preferred size range for satisfactory interstitial contact ofparticles (i.e., binding of absorbent granules together into a cohesiveclump) to result in more easily removable clumps, is about 10 mesh (2.00mm) to about 40 mesh (0.425 mm).

A clumping litter can comprise, for example, about 50% to about 80% byweight core particles comprising an organic substrate, about 0.01% toabout 10.0% by weight of a binding agent impregnating the organicsubstrate, and about 10% to about 40% by weight of a clumping agent,optionally further comprising a polysaccharide gum or a starchcomprising about 1% to about 3% by weight of the litter composition. Thebinding agent binds the clumping agent to the core particles. The ratioof organic substrate to total clumping agents can be, for example, fromabout 2 to 1 to about 4 to 1, or about 2 to 1, about 2.5 to 1, about 3to 1 or about 4 to 1, by weight. Preferably the clumping agent such assodium bentonite is no more than approximately 20% of the product, andany added gum or starch is no more than approximately 2% of the product.While the binding agent can be present at about 0.01% to about 10.0% byweight, certain litters use about 5% or about 7.5% by weight of thebinding agent.

The binding agent binds the clumping agent to the core particles, toprevent or reduce segregation between the clumping agent and the coreparticles. The binding agent comprises for example an aqueous solutionof an adhesive compound, which is preferably water soluble, such that itcan be readily sprayed onto the core particles at relatively lowpressures. The binding agent can comprise for example an aqueoussolution of an adhesive compound, such as but not limited to a polyvinylalcohol, guar gum, tara gum, xanthan gum, a hydrocolloid gum, sodiumalginate, a latex, a starch, corn syrup, corn syrup solids, or anycombination thereof. An aqueous solution of the adhesive compound shouldhave a viscosity suitable for spraying and can contain, for example, aconcentration of the adhesive compound of about 0.1% to about 5%, about0.1% to about 10%, about 0.1% to about 75%, or about 0.1% to about 99%by weight. In exemplary, non-limiting clumping animal litters, theconcentration of the adhesive compound in aqueous solution can be about0.1% to about 5.0% by weight, or about 5% to about 15% by weight.Alternatively, the binding agent can comprise up to about 98% to about99% or even 100% by weight of an adhesive compound in solution, such asin particular (but not limited to) any of the foregoing adhesivecompounds that exist in liquid form at room temperature, such as cornsyrup. It will be appreciated that certain liquid adhesive compoundssuch as corn syrup may require minimal addition of water, or even nowater, to have a viscosity suitable for application to the coreparticles using conventional spraying equipment. While any such bindingagents can be used, exemplary litters use as the binding agent anaqueous solution of polyvinyl alcohol, corn syrup or an aqueous solutionof corn syrup, an aqueous solution of a starch, or an aqueous solutionof a combination of sodium alginate with at least one polysaccharideother than sodium alginate, or any combination thereof. It will furtherbe appreciated that minimizing the amount of moisture added to thelitter during preparation will reduce the drying effort required toachieve a litter with a relatively low moisture content as describedherein. An exemplary binding agent is one that can be suitably preparedfor spraying at a relatively high concentration in aqueous solution,such as corn syrup. In a non-limiting but exemplary clumping animallitter, the ratio of the binding agent(s) to the organic core particlesis less than about 15% by weight.

The clumping agent can comprise any one or more of various gelling orclumping clay and non-clay materials, such as attapulgite, bentonite,kaolinite, sepiolite, a polysaccharide gum, or a starch, or anycombination thereof. A gelling material is absorbent and swells suchthat particles of the material clump together when moistened. Any of thegelling clays such as bentonite can be for example a sodium or calciumclay compound, e.g. sodium bentonite or calcium bentonite. A clumpingmaterial is absorbent and at least provides additional hardening ofclumps formed upon contact of the litter with moisture. An exemplary,non-limiting clumping litter includes sodium bentonite as a clumpingagent, which is optionally combined with polysaccharide gum or starch. Apolysaccharide gum or starch can be borated. A borated material issimply that material mixed with a sodium borate, such as sodiumtetraborate (anhydrous, pentahydrate or decahydrate forms can be used).For example, a borated starch is a starch mixed with a sodium borate. Aborated polysaccharide gum is a sodium borate mixed with apolysaccharide gum. Suitable polysaccharide gums include, but are notlimited to, sodium alginate, guar gum, tara gum, xanthan gum, locustbean gum, cassia gum, and carboxymethyl cellulose. Exemplary,non-limiting starches include wheat starch and potato starch, any ofwhich can be borated. In an exemplary, non-limiting clumping animallitter, the clumping agent comprises sodium bentonite, and optionallyfurther comprises a borated polysaccharide gum or borated starch. Inanother exemplary, non-limiting clumping animal litter, the clumpingagent comprises sodium bentonite, and sodium alginate. In anotherexemplary, non-limiting clumping animal litter, the clumping agentcomprises sodium bentonite and a combination of sodium alginate gum andsodium borate.

A clumping litter including both a clay such as sodium bentonite and aborated gum or borated starch, can for example comprise about 10% toabout 40% by weight of the clay, and a combination of a polysaccharidegum or starch with sodium borate in a weight-to-weight ratio of about80% to about 85% gum or starch (unborated) to about 15% to about 20%sodium borate. For example, a clumping litter may comprise a combinationof sodium bentonite with a combination of sodium alginate gum and sodiumborate combined in a weight-to-weight ratio of about 80% to about 85%sodium alginate gum to about 15% to about 20% borate. Another exemplary,non-limiting clumping animal litter comprises sodium alginate and sodiumborate combined in a weight to weight ratio of about 85% sodium alginategum to about 15% borate. The combination of the gum or starch(unborated) and the sodium borate can comprise, for example, about 1% toabout 3% by weight of the litter composition. For example, a clumpinglitter can comprise sodium alginate and sodium borate which togethercomprise about 1% to about 3% by weight of the litter composition.

Clumping animal litters according to the present disclosure preferablyhave a total final moisture content of no more than about 10% to about20% by weight. Exemplary, non-limiting clumping animal litters have amoisture content of no more than about 15%, preferably no more thanabout 10%, more preferably no more than about 8%, and still morepreferably no more than about 5% by weight. An exemplary, non-limitingclumping animal litters has a moisture content of no more than about 10%to about 12% by weight.

Optionally, clumping animal litters as described herein can furtherinclude an odor control agent, which is also bound to the core particlesby the binding agent. The odor control agent can comprise a powderedmaterial that is mixed with the clumping agent before applying theclumping agent to the core particles. The odor control materials shouldbe applied, for example, in small amounts, such as about 5% or less byweight, to properly adhere to the substrate granules. Thus the odorcontrol agent may comprise about 5% or less by weight of the littercomposition. The odor control agent can be selected from odor absorbentmaterials such as, but not limited to, natural and synthetic zeolites,sodium bicarbonate, and magnesium hydroxide; or an odor maskingfragrance as known in the art, or any combination thereof. Zeolites areknown to be particularly effective in trapping ammonia as well ascertain sulfur odors. Sodium bicarbonate is a general odor absorbent.Magnesium hydroxide has not been previously used in a commercial productfor litter box odor, but has been found to be an effective odorabsorbent and neutralizer.

Other liquid additives can be sprayed onto the core particles either inthe process of adding the clumping agents or after the drying andscreening steps of the manufacturing process, as detailed below.Preferably such additives are applied after drying and screening toavoid loss of the liquid additives due to evaporation or heatdegradation during the drying process. Examples of liquid additivesinclude fragrance oils to further aid with odor control or to give theproduct a pleasant scent, antimicrobial materials to aid in preventingodor formation due to absorbing cat waste, and colorants to provide theproduct with an attractive color.

The following steps are illustrative of a process 300 for preparing aclumping hybrid litter according to the present disclosure, as shown inpart in the flow chart of FIG. 3. Dry, core particles comprising a hard,preferably non-agglomerated organic material are first obtained, orprepared as described above (not shown in FIG. 3). The organic coreparticles are added to a mixer 302. The core particles are sprayed 304with a liquid comprising an adhesive compound. The liquid can be anaqueous solution of an adhesive compound as shown in FIG. 3, or can bean adhesive compound that exists in liquid form at room temperature suchas corn syrup (not shown in FIG. 3) or any combination thereof. Theclumping agent is added 306 and contacts the core particles. Theclumping agent and sprayed core particles are mixed 308. Optionally, aclumping additive such as a borated polysaccharide gum or borated starchcan be added 310, before or simultaneously with the addition of theclumping agent, and mixed with the sprayed core particles. Once mixingis complete, the treated particles are removed from the mixer 312 anddried 314 to a final moisture content as described elsewhere herein. Theresulting dried particles are screened 316 to return litter particles ofthe desired size to produce a finished hybrid clumping litter 318.Oversize particles removed by screening can be recycled 320 into process300 as substrate particles going into the mixer. Excess fines can beremoved during screening 322 and also recycled into process 300.

As further shown in process 400 as shown in the flow chart of FIG. 4,obtaining core particles of organic material may involve a previous stepof preparing organic core particles 402, which may involve screeningorganic particles to obtain particles in a predetermined size range 404and as described herein above, for example of about 8 mesh to about 40mesh, about 10 mesh to about 40 mesh, about 14 mesh to about 20 mesh, orabout 14 mesh to about 40 mesh. More narrow size ranges result in a moreuniform appearance of the litter, and a more tightly bound clump. In anexemplary, non-limiting clumping litter, corn cob grit is used for thecore particles.

Some organic materials used for the core particles may need to bepre-formed, which may involve an agglomeration process to make thedesired size range of rigid particles. Other organic or plant derivedmaterials which can be used include, for example, granules of paper,wood chips or sawdust, walnut shells, peanut hulls, rice hulls, wheatstraw, paper sludge, and diaper fluff. The organic material need only beavailable as a small granular and hard form, comparable to particlesprepared from corncob grit. For example, particles suitable for sprayingwith the binding agent solution can be made by grinding organic materialsuch as peanut hulls and/or soybean hulls to a powder, making pellets ina pellet mill, and then crumbling the pellets to obtain particles of thedesired size. For any materials, particle size range is for example nolarger than about 8 mesh (about 2.4 mm), preferably no larger than about10 mesh (about 2.0 mm), to about 40 mesh (about 0.4 mm). It will beunderstood that smaller particle sizes are preferred for litter intendedfor use by cats because cats prefer smaller particle sizes for digging.The particles can be any shape, such as spherical, elliptical,elongated, flat, or some other irregular shape.

Once obtained, core particles of the desired size are placed in arotating drum, such as an agglomeration drum, or other agglomerating orcoating equipment such as a centrifugal coater, pan agglomerator, discpelletizer, blender, or intensive mixer, such as those commerciallyavailable from Eirich Machine Company, Gurnee, Ill. In non-limitingexample, a Rollo-Mixer® batch mixer commercially available fromContinental Products Corp. (Milwaukee, Wis.) is used.

In a second step, the dry core particles are sprayed 406 with thebinding agent, which can be an aqueous solution of an adhesive compoundor an adhesive compound that exists in liquid form at room temperature,or a combination thereof. The binding agent may be prepared 408previously or prepared at about the same time or just prior to spraying.Spraying step 406 is performed for example with the particles in themixer, and can continue while the particles are rotating in the drummixer or agglomerator or other mixing equipment, for a time and underconditions sufficient for the binding agent to substantially distributeover the surface of the core particles. A predetermined amount ofclumping agent, such as sodium bentonite as shown in FIG. 4, is addedand is mixed 410 with the core particles. Optionally, a clumpingadditive such as a borated polysaccharide gum or borated starch can beadded 412, before or simultaneously with the addition of the clumpingagent. The optional clumping agent can also be mixed with the particles.Optionally, an odor control agent can further be added 414 to themixture. Once mixing is complete, the treated particles are removed fromthe mixer and dried 416 to a final, predetermined moisture content.Optionally, before or after drying 416, additional clumping agent,clumping additive and/or odor control agent(s) can be further added418A, 418B to the mixture. The resulting dried particles are screened420 to return litter particles of the desired size and recycle fines andoversize particles as shown in FIG. 3 to produce a finished hybridclumping litter.

As detailed above, the adhesive compound chosen can be water soluble toproduce an aqueous solution such that it can be sprayed onto the organicsubstrate granules at relatively low pressures. Alternatively, anadhesive compound as described herein that exists as a liquid at roomtemperature, for example corn syrup, can be used at approximately 98%,99% or even 100% concentration in the spraying step. While it has beenfound that merely wetting the core particles with a relatively smallamount water at about 5% to 20% by weight of the litter compositionresults in reasonable adherence of the clumping agent to the coreparticles, at the same time the use of an adhesive compound promotesfurther adherence of the clumping agent, reduces the water needed, andalso promotes clump formation by the finished product. Additionally, thefinal drying step, detailed below, further removes water and thusreduces adherence of the clumping agent when only water is used toadhere the clumping agent to the core particles.

The binding agent can comprise the adhesive compound in aqueous solutionat a concentration of about 0.1% up to about 98-99% or about 100% byweight. In non-limiting example, the aqueous solution consists of theadhesive compound dissolved in water at a concentration of about 0.1 to2.0%, by weight. In another non-limiting example, the aqueous solutionconsists primarily of the adhesive compound dissolved in water at aconcentration of about 75% to about 99% by weight. In exemplary,non-limiting methods for preparing a clumping animal litter, theconcentration of the adhesive compound in aqueous solution can be about0.1% to about 5.0% by weight, about 5% to about 15% by weight, or about75% to about 99% by weight. When applied to the core particles, thefinal ratio of adhesive solids to core particles is, for example, nomore than about 2% and preferably less than about 0.1%, by weight. Theaqueous adhesive solution is applied such that the moisture of theproduct increases by no more than about 20%, preferably no more thanabout 10% to about 15%, and more preferably no more than about 0% toabout 10% It should be understood that reducing the amount of moistureadded during manufacturing will reduce the drying time required or eveneliminate the need for a drying step completely, thereby reducing energycost and time required in general. It should further be noted thatanother advantage of the litters and processes described herein is therelatively low amount of moisture used during processing, and thusreduced drying requirement, compared to those required for makingcompletely coated litter particles.

The sprayed core particles are subsequently contacted with an amount ofpowdered clumping agent sufficient for the clumping agent to adhere toonly a portion of the surface of each core particle. The time and/orconditions needed for this step can be readily determined by one ofroutine skill based on visual inspection of the core particles as theyare mixed with the clumping agent. The core particles of organicsubstrate will have a color distinct from the color of the clumpingagent. For example, sodium bentonite is essentially gray, while organicparticles of corn, wood and the like generally have a yellowish orbrownish color. Mixing should cease at least before the point that theparticles are obviously coated completely and exhibit only the color ofthe clumping agent used. In an exemplary method, mixing should ceasewhile the core particles still retain the general color and appearanceof the core particles being used, with perhaps a slight graying ormuddying of initial color due to particles of the clumping agent beingrandomly dispersed on the particle surfaces. It should be noted howeverthat time is not necessarily a determining factor for avoiding acomplete coating of the core particles with the clumping agent. Theamount of time required in the mixer to achieve a partial coating is, innon-limiting example, only about 1 min to about 5 min. Rather, therelative amount of clumping agent compared to the amount of coreparticles limits the ability of the clumping agent to form a completecoat on the core particles. It will be understood that within thebroader range of about 10% to about 40% by weight of the clumping agent,a lower amount of the clumping agent relative to the amount (by weight)of the core particles, provides less material and thus less likelihoodof even being able to achieve a complete coating. According to thepresent disclosure however, the relative amounts of clumping agent andcore particles described herein have been found to provide clumpingperformance comparable to that exhibited by 100% sodium bentonite.Clumping performance can be readily tested using synthetic urine (mix ofvarious salts and urea), actual cat urine, or a 2% sodium chloridesolution.

It has been found that the mixing step should be performed only afterthe core particles have been sprayed with a liquid solution containingthe binding agent, and that the binding agent and clumping agent shouldnot be combined first and then applied to the core particles, or elsethe clumping agent does not sufficiently adhere to the core particles.For example, following spraying, the wet core particles are rotating inthe drum and a pre-determined amount of the clumping agent as a drypowder is added to the rotating drum. The clumping agent can bedispensed into the drum with a screw feeder, for example. Typically theclumping agent, such as for example sodium bentonite, is a powderconsisting of particles having a size of less than 100 mesh (0.150 mm)and preferably less than 200 mesh (0.075 mm). In exemplary method forpreparing a clumping litter using corncob grit as the core particles,and sodium bentonite as a clumping agent, the amount of sodium bentonitein the litter is about 10% to about 40% by weight, preferably about 20%to 25% by weight, to achieve good clumping strength while minimizing useof the sodium bentonite.

In alternative clumping litters, a gum may be combined with a firstclumping agent and added to the drum or other mixer at about the sametime with the first clumping agent. For example, a gum, such as boratedsodium alginate, can also be added simultaneously with a separate screwfeeder, when a first clumping agent such as sodium bentonite is beingadded as described above. Alternatively, the gum can be premixed withthe first clumping agent such as sodium bentonite, and the combinationadded to the drum or other mixer using a single screw feeder. When used,such gums comprise a dry powder having a particle size of less thanabout 30 mesh (about 0.6 mm) and preferably less than about 50 mesh(about 0.3 mm). A gum used in combination with a first clumping agentsuch as sodium bentonite can comprise about 1 to 3% by weight, andpreferably about 1 to 2% by weight of the litter composition.

After the mixing and is complete, the product exits the mixer oragglomerator and is dried to a predetermined moisture content, usuallyless than about 20%, and preferably less than about 15%, by weight. Anexemplary but non-limiting range of moisture content is about 8-12%, orabout 10% to about 12% by weight. Another exemplary but non-limitingrange of moisture content is no more than about 10% to about 20% byweight. Drying can occur in any drying equipment as recognized in theart, such as a rotary dryer, fluid bed dryer, or tray dryer.Alternatively, drying can be performed within a mixer or other mixingequipment by passing hot air through the mixer while the product isbeing mixed, or after the product is mixed. Preferably, a minimal amountof moisture is added to the litter during preparation such thatrelatively little drying is required to achieve a litter with a desiredmoisture content. Preferably, the excess moisture removed is less than20% by weight and preferably only about 10% by weight, for a rapid andefficient drying process. The product is then screened to the desiredsize range of 10 mesh (2.00 mm) to 40 mesh (0.425 mm) to remove anyexcess fines and oversized particles. Excess additive fines (less than40 mesh) can be recycled back into the mixing/coating process. Anyoversized particles (for example, particles greater than 10 mesh) can berecycled back to be milled down to less than about 10 mesh and thenre-enter the process. This method produces a litter product that afterdrying and screening is an effective clumping litter that has arelatively low density in the 20-35 lbs./cu-ft. range. The foregoingmethod can be readily used or adapted to prepare any of the littersdescribed herein.

The foregoing method can be used to combine the components in amountssuch that the core particles comprise about 50% to about 85% by weightof the litter, the binding agent comprises about 0.01% to about 10.0% byweight of the litter, and the clumping agent comprises about 10% toabout 40% by weight of the litter. The adhesive compound can be applied,for example, to the core particles in an amount sufficient to produce inthe clumping litter composition a weight to weight ratio of less thanabout 15% of the adhesive compound to the organic material.

EXAMPLES

The following example(s) are included to demonstrate the disclosure. Itshould be appreciated by those of skill in the art that the techniquesdisclosed in the following examples represent techniques discovered bythe inventors to function well in the practice of the disclosure. Thoseof skill in the art should, however, in light of the present disclosure,appreciate that many changes could be made and still obtain a like orsimilar result without departing from the spirit and scope of thedisclosure. Therefore all matter set forth is to be interpreted asillustrative and not in a limiting sense.

Example 1 Hybrid Clumping Animal Litter

Corncob granules in a size range of 14 mesh (1.40 mm) to 40 mesh (0.425mm) were sprayed with about a 0.5% aqueous solution of sodium alginatecombined with other polysaccharides. The adhesive liquid to corncobgranule ratio was 1 part aqueous solution to 20 parts corncob granules.This resulted in about 0.025% by weight adhesive solids on the corncobgranule surfaces. Immediately after wetting the particles in a panmixer, a mixture of sodium bentonite and borated sodium alginate (e.g.,about 85% sodium alginate combined with about 15% sodium borate) wasadded in a ratio of 30 parts sodium bentonite and 2 parts borated sodiumalginate to 100 parts corncob granules by weight. This translates toabout 30% by weight sodium bentonite and about 2% by weight boratedalginate added to the corncob granules.

After mixing for about 30 seconds the product was dried to a moisturevalue of about 10% and then screened to a 14 mesh (1.40 mm) by 40 mesh(0.425 mm) product to remove any oversized aggregates and excessclumping additive fines.

The final product had a bulk density of about 24 lbs./cu-ft.

Example 2 Clumping Performance

Hybrid clumping animal litter from Example 1 was tested for clumpingperformance using a saline solution consisting of 2% sodium chloride tosimulate cat urine. A volume of 10 ml of the saline solution was droppedonto the litter in a pan to form clumps. After 1 hour the clumps wereremoved and their strength tested using a Chatillon force gauge. Thismeasures how much compressive strength is required to break the clumps.Two commercially available clumping cat litters that contain corncobgranules were also tested for comparison. Results are listed in Table 1.The clump strengths for the corncob product made by this process areeither better than or at least comparable to any natural plant derivedor alternative clumping cat litters currently on the market. Due to therelatively low density of the product the amount of material on a weightbasis necessary to absorb the simulated urine is less than what would berequired if the litter was based entirely on sodium bentonite. Thisproduct absorbed about 90 to 100% of its weight versus about 45% for aclay litter using sodium bentonite as the clumping agent.

TABLE 1 Comparative Clump Strength Arm & Hammer Tidy Cats ® Pure NaturalNature (mixture Clump Strength Hybrid Essentials ® of corncob, pine,(lbs of force) - clumping (corncob and and cedar with gum after 1 hourlitter guar gum) clumping agent) Avg from 3 1.16 0.63 0.93 clumps

Example 3 Hybrid Clumping Animal Formulations

Hybrid clumping litters according to the following formulations havebeen made following the process outlined in Example 1.

TABLE 2 Litter Formulations Typical % % By Ingredient By Weight WeightRange Substrate - corncob 69.5 50-85% granules, peanut hull granules,soybean hull granules Corn Syrup Binder 7.5 of  1-15% (concentratediluted in water concentrate 50:50 or other dilutions up to 75:25) Canuse PVA or other water- soluble adhesive binders. Sodium Bentonite -primary 20% 15-30% clumping agent Clumping Aid - wheat starch  3%  0-5%mixed with sodium tetraborate (anhydrous or pentahydrate ordecahydrate). An exemplary mix is 80% starch and 20% borate. Otherclumping aids to use include various hydrocolloids, such sodiumalginate, guar gum, etc.

Example 4 Hybrid Clumping Animal Formulations

Hybrid clumping litters using corncob core particles, corn syrup as theadhesive material for the binding agent, and a mixture of sodiumbentonite and borated wheat starch for the clumping agent, were madefollowing the process outlined in Example 1.

TABLE 3 A corncob-based hybrid clumping litter formulation Ingredient %By Weight Lbs/200 lb. Batch Substrate (corncob) 69.5 139 Corn SyrupBinder Spray at 15% of 30 of diluted (concentrate diluted total productbinder (15 50% in water) weight (7.5% actual binder) actual corn syrup)Sodium Bentonite 20% 40 Mixture of Wheat  3% 6 Starch and Sodium Borate(Premixed)

Example 5 Hybrid Clumping Animal Formulations

Hybrid clumping litters using corncob core particles, corn syrup as theadhesive material for the binding agent, and sodium bentonite (withoutborated wheat starch) for the clumping agent, were made following theprocess outlined in Example 1.

TABLE 4 A corncob-based hybrid clumping litter formulation Ingredient %By Weight Lbs/200 lb. Batch Substrate (corncob) 67.5 135 Corn SyrupBinder 15% of total 30 of diluted (concentrate diluted product weightbinder (15 50% in water) (7.5% corn syrup) actual binder) SodiumBentonite 25%  50

Example 6 Hybrid Clumping Animal Formulations

Hybrid clumping litters using peanut hull core particles, corn syrup asthe adhesive material for the binding agent, and a mixture of sodiumbentonite and borated alginate for the clumping agent, were madefollowing the process outlined in Example 1.

TABLE 4 A peanut hull-based hybrid clumping litter formulationIngredient % By Weight Lbs/200 lb. Batch Substrate (peanut hulls) 67.5139 Corn Syrup Binder 15% of total 30 of diluted (concentrate dilutedproduct weight binder (15 50% in water) (7.5% corn syrup) actual) SodiumBentonite 22% 44 Borated Alginate  1% 2

What is claimed is:
 1. A clumping animal litter comprising: (a) coreparticles consisting essentially of an organic substrate, the coreparticles having an external surface; (b) a binding agent applied to theexternal surface of the core particles; and (c) a clumping agent appliedto the external surface of the core particles, wherein the clumpingagent is adhered by the binding agent to the external surface of thecore particles, the clumping agent optionally further comprising aborated polysaccharide gum or a borated starch; wherein the littercomprises about 50% to about 85% by weight of the core particles, about0.01% to about 10% by weight of the binding agent, and about 10% toabout 40% by weight of the clumping agent, and optionally about 1% toabout 3% by weight of the borated polysaccharide gum or borated starch,and wherein the ratio of the core particles to clumping agents in theanimal litter is about 2.5 to 1 to about 4 to
 1. 2. A clumping animallitter according to claim 1, wherein the binding agent is non-uniformlydistributed over the external surface of the core particles.
 3. Aclumping animal litter according to claim 1, wherein the clumping agentcomprises no more than about 20% by weight of the litter.
 4. A clumpinganimal litter according to claim 1, wherein the organic substrate isselected from the group consisting of corn cob, corn meal, soybean,soybean meal, wheat meal, wheat straw, alfalfa meal, peanut hulls, ricehulls, walnut shells, paper, paper sludge, pine sawdust, diaper fluff,and any combination thereof.
 5. A clumping animal litter according toclaim 1, wherein the organic substrate comprises corncob grit.
 6. Aclumping animal litter according to claim 1, wherein the core particleshave a size of about 8 mesh to about 40 mesh.
 7. A clumping animallitter according to claim 1, wherein the binding agent comprises anaqueous solution of an adhesive compound.
 8. A clumping animal litteraccording to claim 7, wherein the adhesive compound is selected from apolyvinyl alcohol, guar gum, tara gum, xanthan gum, a hydrocolloid gum,sodium alginate, a latex, a starch, corn syrup, corn syrup solids, andany combination thereof.
 9. A clumping animal litter according to claim7, wherein the adhesive compound is selected from a polyvinyl alcohol, astarch, and a combination of sodium alginate with at least onepolysaccharide other than sodium alginate.
 10. A clumping animal litteraccording to claim 7, wherein the concentration of the adhesive compoundin the aqueous solution is about 0.1% up to about 5% by weight, insolution.
 11. A clumping animal litter according to claim 7, having aratio of the adhesive compound to the core particles of less than about15% by weight.
 12. A clumping animal litter according to claim 7, havinga moisture content of no more than about 10% to about 20% by weight. 13.A clumping animal litter according to claim 1, wherein the clumpingagent comprises a material selected from attapulgite, sodium bentonite,kaolinite, sepiolite, or any combination thereof, and further comprisesa borated polysaccharide gum, and a borated starch, or any combinationthereof.
 14. A clumping animal litter according to claim 13, wherein theclumping agent comprises sodium bentonite and further comprises boratedwheat starch.
 15. A clumping animal litter according to claim 1, furthercomprising an odor control agent comprising about 5% or less by weightof the litter composition.
 16. A clumping animal litter according toclaim 15, wherein the binding agent further binds the odor control agentto the core particles.
 17. A clumping animal litter according to claim15, wherein the odor control agent comprises at least one materialselected from natural and synthetic zeolites, sodium bicarbonate, andmagnesium hydroxide.
 18. A clumping animal litter according to claim 1,wherein: the organic substrate comprises corn cob grit; the clumpingagent is sodium bentonite and further comprises borated wheat starch;and the binding agent is corn syrup; wherein the litter comprises about69.5% by weight corn cob grit, about 20% by weight sodium bentonite,about 3% by weight borated wheat starch, and about 7.5% by weight ofcorn syrup.